CN101420815B - Amplitude discriminating sensor, radio frequency transmission system and method for load resistance amplitude discrimination - Google Patents

Abstract

The invention discloses an amplitude discrimination sensor, a radio frequency transmission system and a method for carrying out the amplitude discrimination of load impedance, wherein, the amplitude discrimination sensor is connected on a radio frequency main transmission line of the radio frequency transmission system, a voltage signal acquisition unit and a current signal acquisition unit of the amplitude discrimination sensor respectively acquire a voltage signal and a current signal of the radio frequency main transmission line, then the voltage signal and the current signal are received by an analog multiplier, the received signals are calculated, the signals after the calculation are input to a controller, and the controller carries out the calculation of the received signals to obtain the amplitude of the load impedance, thereby realizing the amplitude discrimination of the load impedance of the radio frequency transmission system. The performance precision is high, and the reliability is high.

Description

Amplitude discrimination transducer and radio-frequency (RF) transmission system and load impedance is carried out the method for amplitude discrimination

Technical field

The present invention relates to a kind of semiconductor processing technology, relate in particular to a kind of amplitude discrimination transducer and radio-frequency (RF) transmission system and load impedance is carried out the method for amplitude discrimination.

Background technology

Plasma is widely used in the production of semiconductor device.In plasma etching system, radio-frequency power supply is powered to produce plasma to plasma chamber.The atom, molecule and the free radical isoreactivity particle that contain a large amount of electronics, ion, excitation state in the plasma, these active particles interact with the wafer that places cavity and expose to the open air under plasma environment, make the wafer material surface that various physics and chemical reaction take place, thereby the material surface performance is changed, finish the etching process of wafer.

Radio-frequency power supply operating frequency commonly used is 13.56MHz, and output impedance is 50 Ω, is that the coaxial cable of 50 Ω links to each other with reaction chamber by characteristic impedance.Along with the carrying out of etching process, gas componant in the chamber and pressure is all in continuous variation, therefore, as the isoionic impedance of load also in continuous variation.And the internal resistance of radio-frequency power supply is 50 fixing Ω, and promptly impedance is unmatched between power source and the load, so just causes having bigger reflection power on RF (radio frequency) transmission line, and radio frequency power output can't all be applied to plasma chamber.If the RF energy shortage that obtains is so that plasma glow start, etching process just can't be carried out, and power is understood the reflected back power supply, when reaching 20% left and right sides of power output, will damage the RF power supply.

As shown in Figure 1, prior art is to insert a matching network between RF power source and plasma chamber, makes load impedance and source impedance can reach conjugate impedance match.Because along with the carrying out of etching process, the value of load impedance is constantly to change, need to introduce an impedance magnitude, phase detectors, i.e. transducer (Sensor).By the voltage on the sense transmission line, current signal, utilize certain amplitude discrimination and phase detecting method, just can obtain the amplitude and the phase place of load impedance.The automatic impedance controller is according to the output of transducer, the rotation of control step motor, thus adjust variable element in the matching network, the total impedance that finally makes matching network and plasma cavity is 50 Ω, the realization impedance matching.

As shown in Figure 2, balanced type amplitude discrimination method of the prior art:

According to the voltage and current input load impedance amplitude on the transmission line, the voltage and current signal that takes out from the RF transmission line (is made up of resistance capacitance by diode and filter circuit, do not draw among Fig. 2, the with dashed lines replacement) carries out rectifying and wave-filtering, obtain the D. C. value of voltage and current sampled signal, be respectively Mag+ and Mag-, by the connection of diode among Fig. 2 as can be seen: (Mag+)＞0, (Mag-)＜0.Mag+ and Mag-are added to the two ends of potentiometer R respectively, just can judge the situation of load impedance amplitude by the magnitude of voltage of measuring potentiometer R centre cap place, promptly have: when the amplitude of load impedance | during Z|=50 Ω, the magnitude of voltage MAGNITUDE=0 at potentiometer R centre cap place is arranged then; When | Z|＞50 Ω, MAGNITUDE＞0; When | Z|＜50 Ω, MAGNITUDE＜0.

There is following shortcoming at least in above-mentioned prior art: because the consistency of diode characteristic is difficult to assurance, so its precision performance is low, and the circuit volume is big, and consistency is poor, and reliability is low.

Summary of the invention

The purpose of this invention is to provide a kind of precision performance height, reliability high amplitude discrimination transducer and radio-frequency (RF) transmission system and load impedance is carried out the method for amplitude discrimination.

The objective of the invention is to be achieved through the following technical solutions:

Amplitude discrimination transducer of the present invention, comprise signal gathering unit, described signal gathering unit comprises voltage signal acquisition unit and current signal collecting unit, the output of described voltage signal acquisition unit and current signal collecting unit is connected with analog multiplier respectively, described analog multiplier can receive alternating voltage or ac current signal, and the output expression formula of described analog multiplier is:

Formula 1: $\mathrm{Vout}=\frac{(X1-X2)(Y1-Y2)}{10}+Z2$ In the formula: X1, X2, Y1, Y2, Z2 are input variable.

Radio-frequency (RF) transmission system of the present invention, comprise the radio frequency main transmission line, be connected with claim 1 or 2 described amplitude discrimination transducers on the described radio frequency main transmission line, the voltage signal acquisition unit of described amplitude discrimination transducer and current signal collecting unit are coupled with described radio frequency main transmission line respectively, the output of described amplitude discrimination transducer is connected with controller

The amplitude of the load impedance of the described radio-frequency (RF) transmission system of calculated signals that described controller transmits according to described amplitude discrimination transducer, the calculation expression of described controller is:

Formula 2: $\left|Z\right|=k\sqrt{A0/\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="S2007101762322E00021.png"\; state="\{\{state\}\}">A</figure-callout>}1}$ In the formula: k is a constant; A0 and A1 are respectively described voltage signal and the output signal of current signal after described amplitude discrimination transducer is handled.

Of the present invention the load impedance of above-mentioned radio-frequency (RF) transmission system is carried out the method for amplitude discrimination, comprises step:

At first, ac voltage signal and the ac current signal on the radio frequency main transmission line of detection radio-frequency (RF) transmission system;

Then, described ac voltage signal for the input variable X1 in people's formula 1, Y1, and is made as 0 with the X2 in the formula 1, Y2, Z2, carries out computing; With same method with described ac current signal in people's formula 1, carry out computing;

Afterwards, with the result of computing for the amplitude of calculating described load impedance in people's formula 2.

As seen from the above technical solution provided by the invention, amplitude discrimination transducer of the present invention and radio-frequency (RF) transmission system and load impedance is carried out the method for amplitude discrimination, because analog multiplier can receive AC signal, the amplitude discrimination transducer can detect alternating voltage and the current signal on the radio frequency main transmission line of radio-frequency (RF) transmission system; Then, carry out computing by 1 pair of described alternating voltage of formula and current signal, and calculate the amplitude of the load impedance of described radio-frequency (RF) transmission system according to the result of computing by formula 2 by analog multiplier.Precision performance height, reliability height.

Description of drawings

Fig. 1 is a radio-frequency (RF) transmission system block diagram of the prior art;

Fig. 2 is the circuit theory diagrams of balanced type amplitude discrimination in the prior art;

Fig. 3 is the theory diagram of amplitude discrimination transducer of the present invention and radio-frequency (RF) transmission system;

Fig. 4 is the circuit theory diagrams of analog multiplier among the present invention.

Embodiment

Amplitude discrimination transducer of the present invention and comprise the radio-frequency (RF) transmission system of this transducer, its preferable embodiment as shown in Figure 3,

Be connected with the amplitude discrimination transducer on the radio frequency main transmission line of radio-frequency (RF) transmission system, the amplitude discrimination transducer comprises signal gathering unit, analog multiplier, and the signal gathering unit collection signal of telecommunication inputs to analog multiplier and handles.

As shown in Figure 4, analog multiplier can receive AC signal, comprises ac voltage signal, current signal, and the output expression formula of analog multiplier is:

$\mathrm{Vout}=\frac{(X1-X2)(Y1-Y2)}{10}+Z2---\left(1\right)$ In the formula: X1, X2, Y1, Y2, Z2 are input variable.

The output of analog multiplier can also be connected with low pass filter.

The signal gathering unit of amplitude discrimination transducer comprises voltage signal acquisition unit and current signal collecting unit, gathers the voltage signal and the current signal of radio frequency main transmission line respectively.

The output of amplitude discrimination transducer is connected with controller, the amplitude of the load impedance of the calculated signals radio-frequency (RF) transmission system that controller transmits according to the amplitude discrimination transducer.

The calculation expression of controller is:

$\left|Z\right|=k\sqrt{A0/A1}---\left(2\right)$ In the formula: k is a constant; A0 and A1 are respectively voltage signal and the output signal of electric current current signal after the amplitude discrimination transducer is handled.

Of the present invention the load impedance of above-mentioned radio-frequency (RF) transmission system is carried out the method for amplitude discrimination, comprises step:

At first, ac voltage signal and the ac current signal on the radio frequency main transmission line of detection radio-frequency (RF) transmission system;

Then, described ac voltage signal for the input variable X1 in people's formula 1, Y1, and is made as 0 with the X2 in the formula 1, Y2, Z2, carries out computing; With same method with described ac current signal in people's formula 1, carry out computing;

Afterwards, with the result of computing for the amplitude of calculating described load impedance in people's formula 2.

With the result of computing for people's formula 2 before, can be at first the result of computing be carried out filtering, remove frequency-doubled signal.

Specific embodiment:

Referring to Fig. 3, adopt two analog multipliers to detect the amplitude of load impedance.An analog multiplier be input as the voltage sine wave signal that takes out from RF (radio frequency) transmission line, another analog multiplier be input as the current sinusoidal ripple signal that takes out from the RF transmission line.Through after the processing of analog multiplier, the signal of output carries out next step processing through inputing to controller after the filtering of RC low pass filter.

Suppose with the voltage sampling signal to be reference, if the voltage signal that takes out from the RF transmission line on the amplitude discrimination transducer is u (t)=Ucos ω t, current signal is i (t)=Icos (ω t-θ), wherein U, I are respectively the amplitude of voltage and current signal, θ is the phase place that electric current lags behind voltage, ω is an angular frequency, and t is the time.

Output expression formula according to analog multiplier MPY634: $\mathrm{Vout}=\frac{(X1-X2)(Y1-Y2)}{10}+Z2---\left(1\right)$

In conjunction with Fig. 4, the transitive relation formula that can obtain analog multiplier U1 thus is as follows again:

$\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="S2007101762322E00021.png"\; state="\{\{state\}\}">U</figure-callout>}1\mathrm{out}=\frac{U\cos \mathrm{\&omega;t}\&CenterDot;U\cos \mathrm{\&omega;t}}{10}=\frac{1}{20}{U}^2(1+\cos 2\mathrm{\&omega;t})---\left(3\right)$

The RC low-pass filter network of U1out signal through being made of resistance and electric capacity removed 2 frequency-doubled signals $\frac{1}{20}{U}^2\cos 2\mathrm{\&omega;t},$ The direct current signal that arrives dsp controller is

$A0=\frac{1}{20}{U}^2---\left(4\right)$

Equally, for analog multiplier U2, its transitive relation is shown below:

$U2\mathrm{out}=\frac{I\cos (\mathrm{\&omega;t}-\mathrm{\&theta;})\&CenterDot;I\cos (\mathrm{\&omega;t}-\mathrm{\&theta;})}{10}=\frac{1}{20}{I}^2(1+\cos 2(\mathrm{\&omega;t}-\mathrm{\&theta;}))---\left(5\right)$

The RC low-pass filter network of U2out signal through being made of resistance and electric capacity removed 2 frequency-doubled signals $\frac{1}{20}{I}^2\cos 2(\mathrm{\&omega;t}-\mathrm{\&theta;}),$ The direct current signal that arrives dsp controller is

$\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="S2007101762322E00021.png"\; state="\{\{state\}\}">A</figure-callout>}1=\frac{1}{20}{I}^2---\left(6\right)$

Controller carries out computing to signal A0 and A1, can obtain the amplitude of load impedance | and Z| is

$\left|Z\right|=k\frac{U}{I}=k\frac{\sqrt{20\&CenterDot;A0}}{\sqrt{20\&CenterDot;\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="S2007101762322E00021.png"\; state="\{\{state\}\}">A</figure-callout>}1}}\text{=k}\sqrt{A0/A1}---\left(2\right)$

In the following formula, k is a proportionality constant, and is relevant with current amplitude I with voltage amplitude U.

The amplitude discrimination method that relates among the present invention is not very strict to the requirement of input signal, not needing sampled voltage and current sinusoidal ripple conversion of signals is direct current signal, therefore reduced the circuit of sinusoidal wave commentaries on classics direct current signal, performance maintain an equal level or more excellent prerequisite under reduced circuit complexity and volume greatly, amplitude discrimination is realized by the integrated chip analog multiplier, therefore improved precision, consistency and the reliability of circuit, system realizes than being easier to.Can well detect the amplitude of load impedance.Just can well judge the amplitude of load impedance by formula (2) | Z|.

The output of analog multiplier can be given controller and be handled, and also can give other arithmetic element and carry out the amplitude that computing obtains load impedance | Z|.

Be applicable to that frequency is the radio-frequency (RF) transmission system of 13.56M, also is applicable to the radio-frequency (RF) transmission system of 0.325-100M frequency range.

The above; only for the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, and anyly is familiar with those skilled in the art in the technical scope that the present invention discloses; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.

Claims (3)

1. a radio-frequency (RF) transmission system comprises the radio frequency main transmission line, it is characterized in that, is connected with the amplitude discrimination transducer on the described radio frequency main transmission line;

Described amplitude discrimination transducer comprises signal gathering unit, described signal gathering unit comprises voltage signal acquisition unit and current signal collecting unit, the output of described voltage signal acquisition unit and current signal collecting unit is connected with analog multiplier respectively, described analog multiplier can receive ac voltage signal or ac current signal, and the output expression formula of described analog multiplier is:

Formula 1:

In the formula: X1, X2, Y1, Y2, Z2 are input variable;

The output of described analog multiplier is connected with low pass filter;

The voltage signal acquisition unit of described amplitude discrimination transducer and current signal collecting unit are coupled with described radio frequency main transmission line respectively, and the output of described amplitude discrimination transducer is connected with controller;

The amplitude of the load impedance of the described radio-frequency (RF) transmission system of calculated signals that described controller transmits according to described amplitude discrimination transducer, the calculation expression of described controller is:

Formula 2: In the formula: k is a constant; A0 and A1 are respectively described ac voltage signal and the output signal of ac current signal after described amplitude discrimination transducer is handled.

2. one kind is carried out the method for amplitude discrimination to the load impedance of the described radio-frequency (RF) transmission system of claim 1, it is characterized in that, comprises step:

At first, ac voltage signal and the ac current signal on the radio frequency main transmission line of detection radio-frequency (RF) transmission system;

Then, described ac voltage signal for the input variable X1 in people's formula 1, Y1, and is made as 0 with the X2 in the formula 1, Y2, Z2, carries out computing; With same method with described ac current signal in people's formula 1, carry out computing;

Afterwards, with the result of computing for the amplitude of calculating described load impedance in people's formula 2.

3. according to claim 2 the load impedance of described radio-frequency (RF) transmission system is carried out the method for amplitude discrimination, it is characterized in that, with the result of computing for people's formula 2 before, at first the result to described computing carries out filtering, removes frequency-doubled signal.

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